Multiple security issues have been found in Thunderbird: Multiple memory safety errors and use-after-frees may lead to the execution of arbitrary code or denial of service.
For the stable distribution (stretch), these problems have been fixed in version 1:60.2.1-2~deb9u1.
We recommend that you upgrade your thunderbird packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/